Shimming Your Rear Springs

Time: 1 hour

Tools: standard socket set, standard wrenches

Cost: Fabrication costs will vary, but expect to pay around $20-$30 to have them made. If you purchase your own material ahead of time, factor in about another $10.

Tinware: A small plate of aluminum stock- 6061 aircraft alloy is the most common and the least expensive.

Tip: You can save some money by making the shims yourself if you have a wide assortment of hole saws or a knockout punch. They may not produce the cleanest results, but will work nonetheless.

Performance gains: none, just the peace of mind knowing your car is sitting level and straight

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Made from a lightweight, yet strong aluminum stock, these rings/spacers are the perfect trick to level out an uneven stance.

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To access the lower spring seat, you must first disconnect the shock absorber and allow the axle to slowly drop- releasing all tension on the coil spring.

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With the spring removed, installing the spacer requires nothing more than dropping it into position at the bottom of the spring seat.

How many times have we all seen a car, either in our driveway or possibly going down the road that is somehow constantly listing or favoring one side? With certain cars and body lines, it can deceivingly be nothing more than an optical illusion. Or is it? Regardless, it’s the little things like this that drive us all crazy.

A while back, I was helping a friend of mine install a new pair of rear coil springs and shocks into his ’68 Buick Skylark. After thoroughly wallowing in the road grime underneath the car, we finally got everything back in place and slowly lowered the car onto the ground. I admit everything appeared to be fine and dandy at first glance. However, when we both took about ten paces back, we could not help but notice a slight rake in the car’s stance. No, I’m not talking about the classic muscle car rake. I mean the car appeared to be sitting as if one of the rear tires was slightly deflated. How can this be? We just completed the install on a brand new set of performance shocks and springs. Well, after retracing our steps and double-checking the work to make sure no bonehead maneuvers were made, we were still scratching our heads. Everything seemed to check out OK as it should. At this point, we brought out the tape measure in an effort to obtain an accurate reading from the ground to the lip of the rear wheel wells. Lo and behold, we had a problem. Taking our measurements from several different locations on a flat, true surface (as true as it gets anyway), it was determined that the rear right hand side of the car sagged or sat lower by a half an inch.

This old Buick had a rough life– door dings galore, plenty of rust, some mysterious (how did that happen?) dents, and a Texas hail storm on the hood. Sound familiar? As with many, there is really no telling what happened to this once clean and pristine car.

Although there were grand plans for someday totally overhauling the car, the budget at the time was not quite there. In the meantime, we might as well do what we can, right? Aligning the rear end for a solid, even stance would be priority one. We decided to test our fabrication skills at making a couple of shims or spacers to quick fix this nagging problem. The best way we found was to actually make a template out of cardboard first, measuring the overall diameter of the spring seat as well as the diameter of the inside retainer.

With the help of a local machine shop, we were able to duplicate the cardboard template using the aluminum we had previously purchased. On a machine lathe and mill, the job instantly becomes a walk in the park for any veteran machinists. It’s beautiful– they slice and dice the raw alloy like butter! Approximately 15 minutes and twenty dollars later, we had our magic shims in hand and were ready to put them to the test.

Made from a lightweight, yet durable aircraft aluminum, the spacers simply drop down inside the spring seat underneath the bottom coil. Depending on your car and literally how off-kilter it may be, you may need to use multiple shims or a thicker stock alloy to correct the offset. With the shim(s) in place, re-install the spring and shock absorber. Lower the car back onto the ground and repeat your measurements. Remember, driving the car will naturally help things to settle a bit, so give it some time and check it again.

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